DE2947824A1 - CROSS-SECTION STABLE, HYGROSCOPIC CORE / SHEATH STRUCTURE, FIBERS AND THREADS AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Abstract

Hygroscopic filaments or fibers with a core-jacket structure of hydrophobic, filament-forming synthetic polymers having a water retention capacity of at least 10% and having uniform round to oval cross-sectional profiles are obtained by a dry-spinning process which comprises addition of a substance to the spinning solvent which (a) has a higher boiling point than the spinning solvent used, (b) is readily miscible with the spinning solvent and with water, (c) is a non-solvent for the polymer to be spun, and addition of another substance which (a) is soluble in the non-solvent for the polymer to be spun, (b) is soluble in the solvent for the polymer (c) remains dissolved in the non-solvent for the polymer during solidification of the filaments, (d) is insoluble in water, and (e) does not evaporate to any significant extent during the spinning process, to the system in quantities of at least 1% by weight, based on polymer solids/spinning solvent/non-solvent carrying out the spinning process in such a way that the non-solvent does not evaporate to any significant extent in the spinning duct and washing out the non-solvent from the solidified filaments.

Description

BAYER AKTIENGESELLSCHAFT 5090 Leverkusen, Bayerwerk Central area -_

Patents, trademarks and licenses Dn / kl-c C Λ NOV. “979

Cross-sectional stable, hygroscopic core / sheath structure exhibiting fibers and threads and processes for their Manufacturing

In DE-OS 25 54 124 has already been proposed, hygroscopic threads and fibers made of hydrophobic
to produce thread-forming, synthetic polymers by adding 5-50% by weight to the spinning solvent, based on

5 gene on solvent and solid, a substance

adds, which is essentially a nonsolvent for the polymer, which has a higher boiling point than the solvent used and that with the
Spinning solvent and a liquid suitable as a washing liquid for the threads is readily miscible and then washes this nonsolvent out of the threads produced. Preferred nonsolvents in this process are polyhydric alcohols such as glycerin, sugars and glycols.

The threads and fibers obtainable by this process do indeed have excellent water absorbency and have a round to trilobal cross-sectional shape in the spinning material, which, however, in the course of subsequent

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treatment mostly to star-shaped to bizarre profiles collapsed. Main influencing variables, which the cross-sectional shape change are the stretching, drying and steaming processes. Fibers with such bizarre cross-sections - 5 Profiles can turn into fluffy and hairy yarns, rough handle, when they are further processed into textiles or increase the proportion of short fibers due to breaks in the yarn.

The present invention was therefore based on the object of providing hygroscopic fibers and threads with largely uniform to produce round to oval fiber cross-sections, which you can use in the aftertreatment of the spun material Maintain profile and are therefore easier to process into textile structures.

15 It has now surprisingly been found that such Manufacture fibers and filaments having a hygroscopic core / fraction structure using a dry spinning process can, if you add to the system known from DE-OS 25 54 124 polymer solid / spinning solvent / non-

solvent for the polymer solid before the spinning process also introduces a substance, the following Conditions met:

1. it is soluble in the nonsolvent for the polymer solid, e.g. glycols etc.,

2. it is soluble in the spinning solvent, e.g. DMF,

3. It is soluble in the non-solvent even during the thread consolidation,

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4. It is insoluble in water and

5. It does not evaporate during the spinning process.

Substances that meet these requirements are e.g. polymer compounds from the range of polycarbonates, Polystyrenes, Pc * - ■ -, inyl acetates and cellite derivatives.

The invention therefore relates to the method characterized by claims 3 to 6.

According to this process, threads and fibers are obtained from hydrophobic polymers, in addition to the desired uniform round to oval cross-sectional profiles have a water retention capacity of at least 10% and have a Xern / Mantex structure in which the The core is highly microporous, with the pores being predominantly connected to one another and the core surrounding cladding is much more compact compared to the core, but is penetrated by channels that form the Allow access of liquids to the pore system of the core. Threads and fibers with such core / sheath structures are described, inter alia, in DE-OS 25 54 124 and DE-OS 27 19 019 mentioned at the beginning.

The present invention therefore relates to such threads and fibers, which are characterized in that they have uniform round to oval cross-sectional profiles.

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In that the used in the method according to the invention further spinning additives in the nonsolvent for the polymer solids, e.g. glycerine for polyacrylonitrile, remain dissolved during the thread consolidation and are only precipitated on contact with water, fill they remove the pores that are created by washing out the nonsolvent in the threads. By the embedded additives in the pore system of the fibers becomes the cavity structure of such threads, like scanning electron microscopy Recordings show stabilized by the formation of strong cell walls inside the fibers. This effect continues from the fiber core to the outside, so that uniform cross-sectional structures can be obtained. As evidence that such polymeric additives are in the nonsolvent during thread consolidation remain solved, the following observation is made:

If you examine spun material samples in the microscope with transmitted light, they appear bright white as long as they are not come into contact with water. If water is added, however, the additional polymer substance is obtained as a result of precipitation a dark fiber core and light outer cladding. Is used as an additional polymer compound, for example Polycarbonate, it can then be made from e.g.

Quantitatively recover hygoscopic polyacrylonitrile fibers, e.g. by extraction with methylene chloride. If you use compounds that do not meet the conditions mentioned, you will not achieve a cross-section stabilizing one Effect. If, for example, an acrylonitrile homo-

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polymer, this is probably in the spinning solvent DMF soluble, but not in the nonsolvent, for example in glycerine or glycols. After implementation The aftertreatment of spun material into fibers or threads results in bizarre, up to worm-shaped cross-sectional profiles. Like test series with different Concentrations of polymeric additives are shown to be ranging from 1-5% by weight, preferably 1.5-4% by weight, based based on the weight of the polymer solids / spinning solvent and nonsolvent system already to achieve a cross-section stabilizing effect of the fibers.

Another important advantage of the present invention is that such fibers are not limited to the further processing no longer have the disadvantages mentioned at the beginning, but that they additionally have a very stable pore system, which can be used in manufacturing processes such as steaming, ironing and the like is far less sensitive. Furthermore, the spun-in additives cause an increase in the water retention capacity, which contributes to the comfort properties of such fibers.

An additional advantage arises from the fact that the fibers of the invention are also compared to Shrinkage processes during drying are less sensitive and their cross-sectional structure is largely retained. In this way it is possible to have fibers and threads with a hydrophilic core / sheath structure, also in cable form to manufacture on a large scale.

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In tests it also turned out to be a great advantage that such slivers through a drying process Lose moisture much faster and more strongly than slivers without such additives. Through this the flake presentation could be improved and the production output increased not insignificantly.

Determination of the water retention capacity (WR):

The water retention capacity is determined on the basis of DIN regulation 53 814 (cf. Melliand Textile Reports ±, 1973, page 350).

The fiber samples were immersed in water containing 0.1% wetting agent for 2 hours. The fibers were then centrifuged for 10 minutes at an acceleration of 10,000 m / sec ^a and the amount of water retained in and between the fibers was determined gravimetrically. To determine the dry weight, the fibers are dried ^{at 105 ° C. to constant moisture content.} The WR in percent by weight is:

WR = _t tr _{χ 100}

^m tr

nif - weight of the moist fiber material m. * weight of the dry fiber material

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The following examples serve to explain the invention in more detail. Unless otherwise noted, refer to Parts and percentages are based on weight.

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AO

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example 1

a) 10 kg of dimethylformamide with 2.5 kg of polycarbonate (Polykohlensäureester of 4.4 x -Dihydroxydipheny1-2,2-propane MG. ca. dissolved in a vessel with stirring at 13O ⁰ C 80 000). This solution is then metered into a mixture of 50 kg of DMF and 17.5 kg of tetraethylene glycol with stirring at room temperature. Then 20 kg of an acrylonitrile copolymer of the former composition 93.6% acrylonitrile, 5.7% methyl acrylate and 0.7% sodium methallyl sulfonate are added with stirring at room temperature. The amount of polycarbonate added is 2.5%, based on polymer solids / spinning solvent / nonsolvent. The suspension was fed through a gear pump of a heating device and heated to 13O ⁰ C. The residence time in the heating device was 3 minutes. The spinning solution was then filtered and dry-spun in a spinning shaft in a manner known per se from a 240-hole nozzle. The spun material with a titer of 1580 dtex was collected on bobbins and ply into a ribbon with a total of 110 600 dtex. The tow was then dissolved in boiling water 1: stretched 4, Ofach, washed with water at 8O ⁰ C, provided with antistatic preparation and screening drum drier at 100 ⁰ C under voltage dried. The fiber tow leaves the dryer with a moisture content of 41.5%. The cable is then crimped in a stuffer box and here-

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cut into fibers with a staple length of 60 mm. The individual fibers with a final denier of 2.6 dtex have a Strength of 2.2 centi Newton / dtex and an elongation of 32%. The water retention capacity is 46%. As shown by light microscope images magnified 700 times, the fibers have a pronounced core / shell structure with completely uniform round cross-sectional profiles. Like scanning electron microscope Recordings in 1000 times

10 enlargement also show that the pore system is interspersed with strong cell walls 2 - 5μ thick.

b) Part of the fiber tow was branched off, stretched 1: 4.0 times in boiling water, washed, provided with an antistatic preparation and then at different temperatures below Tension or 20% shrinkage approval, dried, crimped and processed into staple fibers. the Table I shows the individual measured variables.

20 As can be seen from Table I, uniformly round to oval cross-sectional shapes are used in all cases obtain.

c) In a further series of experiments, the content of the added amount of polycarbonate was varied to determine from what weight amounts of added substance a cross-section stabilizing Effect in the hygroscopic core / sheath fibers is achieved. The spinning trials were as below

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a) described, carried out. The fiber cross-sections were assessed with a light microscope at a magnification of 700 times. The cross sections were made by embedding obtained in methyl methacrylate. As can be seen from Table II, a cross-section stabilizing occurs Effect from about 1% by weight of added substance.

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Table I.

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No. Post-treatment type ⁰ C Tr.temp /Tension Cable moisture Titer Strength strain WR Transverse ⁰ C Tr.temp / 20% shrinkage after dryer% dtex cN / dtex % % cut ⁰ C Tr.temp / 20% shrinkage profile 1 160 30th 2.4 2.2 26th 45 around
until
oval 2 100 11 2.6 -i. 3 33 46 dto. 3 160 3.2 2.7 2.1 36 24 dto.

Table II

No. Together! setting the Dope in weight? WR Cross-sectional profile 1 Poly-
carbonate Tetraethy-
lenglycol DMF 30th bizarre, star-shaped 2 PAN 0.312 17.5 60 31 worm-like, lobed 3 22.188 0.625 17.5 60 39 round to oval If 21.85 1.25 17.5 60 50 circular 5 21.25 3.0 17.5 60 76 circular 20th 5.0 17.5 60 17.5

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Example 2

a) 10 kg of dimethylformamide are dissolved with 2.5 kg of polyvinyl acetate (Movilith 30) in a vessel with stirring at 12O ⁰ C. This solution is then metered into a mixture of 50 kg of DMF and 17.5 kg of triethylene glycol with stirring at room temperature. Then 20 kg of an acrylonitrile copolymer with the former composition from Example 1 are added with stirring at room temperature. The amount of polyvinyl acetate added is 2.5%, based on polymer solids / spinning solvent / nonsolvent. The suspension was then, as described in Example 1, transferred into a spinning solution, filtered and, as described there, spun into threads and aftertreated into fibers with a final denier of 2.2 dtex. The fiber tow left the dryer with a moisture content of 51%. The fiber strength is 2.6 centi Newtons / dtex, the elongation 30% and the water retention capacity = 52%. As shown by light microscope images magnified 700 times, the fibers have a pronounced core / sheath structure with uniform, round cross-sectional shapes. In the scanning electron microscope, at 1000x magnification, one can see again

25 ke cell walls 2 - 5μ thick in the pore system.

b) Part of the fiber tow was again branched off, stretched 1: 4, O-fold, washed, with antistatic Preparation provided and at different temperatures under tension and shrinkage approval

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dried, curled and processed into staple fibers. The individual measured variables are taken from the table III emerged. As can be seen from Table III, uniform rounds are again obtained in all cases to oval cross-sectional profiles.

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Table III

No. 16Ο ° c Type of follow-up treatment temp. /Tension Cable moisture
after dryer % Tit. He
dtex Strength
c N / dt ex strain
% WH
% Cross-sectional
profile 1 100 ° c Tr. temp / 20 % shrinkage 20th 2.0 3.0 30th 3 ¹ * round to oval 2 160 ° c Tr. temp / 20 % shrinkage 20th 2.2 2.6 32 kO dto. 3 Tr 2.2 2.7 32 21st dto.

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Example 3

a) 60 kg of dimethylformamide are mixed with 2.5 kg of cellite BP 900 (cellite linters esterified with butyric acid), 17/5 kg of glycerine and 20 kg of an acrylonitrile copolymer with the former. Composition from Example 1 at room temperature in a kettle stirred a suspension and then as described in Example 1 in a spinning solution transferred, filtered and the spinning solution spun into threads and fibers with a final titer of 2.3 dtex post-treated. The fiber tow left the dryer with a moisture content of 54%. The fiber strength is 2.6 centi Newton / dtex, the elongation 29% and the water retention capacity 45%. The fibers have a core / shell structure, as shown by light microscope images magnified 700 times with uniform round cross-sectional profiles. You can see in the scanning electron microscope at 1000-fold magnification again strong cell walls 2 - 5u thick in the pore system.

b) Part of the fiber cable was again branched off and, as described in Example 1b, in various ways post-treated. The individual parameters are shown in Table IV. The result is again in all cases uniformly round to oval cross-sectional structures.

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Table IV

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No. ι6ο ⁰ C Post-treatment type temp /Tension cable
after damp
Dryer % Titer
dtex Strength
cN / dt ex strain WB Cross-sectional
profile 1 100 ⁰ C Tr. temp / 20 % shrinkage 26th 3.2 2.6 29 round to oval 2 160 ⁰ C Tr. temp / 20 % shrinkage δ 2.3 2.7 31 [ι O dto. 3 Tr. 3 2.3 2.7 32 19th dto.

CD CX)

Example 4 comparison

a) 60 kg. Dimethylformamide. be .with ^ _; 1 7 <5 _r kg of tetraethylene glycol at room temperature _{rf below f} , stirring in one

Kettle mixed .. Then 20 kg of an acryloni-

'' '' ■ · '': '; "■ - ■:'. '.: i γ ι u; i. Γ.τΓλ Γ'. ·, Τ r.-i ■>: i ■ '

trilcqpolymerisates with the former composition

from Example 1 added and djLe suspension, such as carried out in Example 1, transferred to a spinning solution, filtered and spun into threads. The collected Spinning material is then, as in the example

1 ° 1 set out, aftertreated to fibers with a final titre of 2.7 dtex. The fiber tow left the dryer with a moisture content of 75%. The fiber strength is 2.5 centi Newton / dte *, the elongation is 39% and the water retention capacity = 30%. The fibers are

As shown by light microscope images magnified 700 times, there is a pronounced core / shell structure with bizarre to star-shaped, non-uniform cross-sectional profiles. In the scanning electron microscope, when magnified 1000 times, one can see relatively thin cell walls of 1 - 2 \ i thickness in the pore system.

b) Part of the fiber cable was branched off again

and, as described in Example 1b, variously post-treated. The individual findings are shown in Table V. As a result, you get in all Cases of bizarre, non-uniform to star-shaped fiber cross-sectional structures.

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Table V

to σ ο to

No. ι6ο ⁰ C Post-treatment type temp. /Tension Cable moisture
after dryer % Titer
dtex Strength
cN / dtex strain VR Cross-sectional
profile 1 100 ⁰ C Tr. temp. / 20 % shrinkage 57 2.3 2.4 31 28 star-shaped,
bizarre 2 i6o ⁰ C Tr. temp. / 20 % shrinkage 40 2.6 2.1 38 30th dto. 3 Tr. 14.4 2.6 <-> * - V? 13th dto. very bizarre

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Example 5 Comparison

a) 62.5 kg of dimethylformamide are mixed with 2.5 kg of acrylonitrile homopolymer with a K value of 90, 15 kg of triethylene glycol and 20 kg of an acrylonitrile copolymer with the former. Composition from Example 1 at room temperature in a kettle to form a suspension stirred and then, as described in Example 1, transferred into a spinning solution, filtered and the dope is spun into threads.

As can be determined by preliminary tests, this is used as a cross-section stabilizing additive Acrylonitrile homopolymer is completely insoluble in triethylene glycol, even when heated. The threads are collected again, plied into a cable and, as set out in Example 1, into fibers aftertreated with a final titre of 2.3 dtex. The fiber tow left the dryer with a moisture content of 83%. The fiber strength is 2.7 centi Newtons / dtex, the elongation 35% and the water retention capacity = 38%. The fibers have, like light microscope images in 700-fold magnification show a core / shell structure in inconsistent worm- to rod-shaped bizarre Cross-sectional profiles. In the scanning electron microscope one can see relatively at 1000x magnification thin cell walls of 1 - 2μ thickness in the pore system.

b) Part of the fiber cable was branched off again

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and, as set out in Example 1b, post-treated in various ways. The individual findings are taken from the table VI. As you can see from the table, inconsistent, bizarre,

5 worm-like cross-sectional profiles. An addition to the

Polymer solid / spinning solvent / nonsolvent system only exerts a cross-section-stabilizing effect when it is in the nonsolvent is soluble in the system during the spinning process

remains, and is only precipitated in the course of the aftertreatment, for example by washing, and fills the pore system of the hydrophilic core / sheath fibers from the inside. This also explains the stronger one
Framework structure of the pore system in the form of stronger

Cell walls compared to a porous fiber without such Additive.

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Table VI

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No. Post-treatment type Cable moisture
n. dryer % Titer
dtex ■ Strength
cN / dtex strain
% WR
% Cross-sectional
profile 1 16O C Tr.temp./voltage 50 2.1 2.9 29 27 worm-shaped bizarre 2 100 ⁰ C Tr.temp./20% shrinkage 38 2.5 2.6 39 28 dto. 3 160 ° C dry temperature / 20 % shrinkage 12th 2.3 2.7 36 11 dto.

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Claims (5)

Claims 1.Hygroscopic, core-shell structure exhibiting threads or fibers made of hydrophobic, thread-forming, synthetic polymers with a water retention capacity of at least 10%, characterized by that they have uniform round to oval cross-sectional profiles. 2. Threads or fibers nac vnopru / i 1, characterized in that that the pole _ / .: iere an acrylonitrile polymer 10 ^sat is. 3. Process for the production of hygroscopic threads or fibers having a core-sheath structure with uniform round to oval cross-sectional profiles made of hydrophobic, thread-forming, synthetic see polymers after a dry spinning process, in which one de; r. Spinning solvent adds a substance, the a) has a higher boiling point than the spinning solvent used ti) with the spinning solvent and with water well is miscible c) a nonsolvent for the polymer to be spun represents the spinning process so that the nonsolvent in the spinning shaft does not evaporate substantially Then washes non-solvent from the solidified threads, Le A 20 058 130030/0053 ORIGINAL INSPECTED characterized in that a further substance is added to the system in amounts of at least 1 percent by weight, based on polymer solids / spinning solvent / nonsolvent, adds to that a) is soluble in the nonsolvent for the polymer to be spun, b) is soluble in the solvent for the polymer, c) remains dissolved in the non-solvent for the polymer during the thread consolidation, d) is insoluble in water and e) essentially not evaporated during the spinning process. 4. The method according to claim 3, characterized in that the polymer is an acrylonitrile polymer with at least 40% by weight of acrylonitrile units. 5. The method according to claim 5, characterized in that that the polymer is an acrylonitrile polymer with at least 80% by weight of acrylonitrile units. Le A 20 058 130030/0053